ON THE UNIVERSALITY OF IDEAL ZIMM DYNAMICS OF POLYMERS IN EXTENSIONAL FLOWS.

In a recently reported series of experiments conducted by the Bristol group,**1** minus **3 on polymer elongation in dilute extensional flows, it was found that the critical strain rate epsilon //c at which the coil stretching transition is observed, scales as M** minus **3**/**2 (M being the molecular weight of the polymer). This dependence was observed to hold for nonelectrolytic, flexible polymers in different polymer-solvent combinations, namely, for polystyrene in toluene (for M greater than 0. 8 multiplied by 10**6) and decalin and for polyethylene oxide in water. This paper reviews existing theories on extensional flows of polymer solutions with particular attention to the discrepancy between theory and experiment. The author presents a heuristic deviation of the scaling law in reference to the partially stretched coil (PSC) configuration of free energy of polymer in elongational flow.